1. Technical Field
The present invention relates to a method of manufacturing a semiconductor device including forming a thin film on a substrate and a substrate processing apparatus.
2. Description of the Related Art
As one of the steps of manufacturing a semiconductor device, a thin film forming step can be given, which is the step of forming a thin film such as a silicon nitride film (SiN film) on a substrate. Also, the thin film forming step is the step performed by supplying a processing gas into a processing chamber into which the substrate is loaded. The thin film forming step is performed for the purpose of forming the thin film on a surface of the substrate. However, actually the thin film is formed not only on the surface of the substrate but also on an inner wall of the processing chamber in some cases. When the thin film is deposited thick, a force added thereby is increased to generate cracks and also generate foreign matters (particles) in the processing chamber in some cases. When the foreign matters are placed on the substrate, yield of manufacturing the semiconductor device is deteriorated.
Therefore, there is a need for removing the deposited thin film, every time the thickness of the thin film reaches a certain thickness. In recent years, a dry cleaning method has been preferably used, which is the method for removing a deposit including the thin film by flowing gas called a cleaning gas into the processing chamber. According to this method, there is no necessity for disassembling the processing chamber, the number of cleaning man-hours and a risk of damaging a component can be reduced, and the time required for restarting the thin film forming step can be shortened, to thereby improve an operating ratio of a substrate processing apparatus for executing the thin film forming step (for example see patent document 1).